[ntp:questions] Flash 400 on all peers; can't get ntpd to be happy

Uwe Klein uwe_klein_habertwedt at t-online.de
Mon Mar 14 08:21:22 UTC 2011


unruh wrote:
> On 2011-03-14, Ralph <ralph at depth.net> wrote:
> Nope. The HW clock is a clock which is completely separate from the
> operating system. 
> 
> 
>>So maybe if we could have a mode where ntpd uses the hardware clock to measure the round trip and instead of the system clock? Or just uses the hardare clock 
> 
> 
> Impossible. The HWclock has a precision of only 1 second. And if your
> round trip times are many seconds long, you are in a situation where VM
> are the least of your worries ( eg on a spaceship)
> 
The standard error made here in this group/mlist!

Someone has "time" requirements of a certain accuracy.

Forex "not more than 10s off"

The tool of choice is ntp ( or crony, or..  )
this will be sufficient : ntp allows sync to less than "10s off"

ntp: Check!

actually it is much better than that, a couple of magnitudes.

Now if someone is asking for help with one issue or other
advice is given in
relation to the accuracy that ntp can/should achieve
and
no longer in relation to what the _actual requirement_ for this
use case is/was.

This tends to be aggravated by the fact that help seekers tend to
sit on relevant information ( like VM, OS, ... ) or tell all but not
their initial requirement.

Still this group has on occasion a knack for answering a question not put ;-)


that said.
In a low accuracy requirement
have the VM machine clock run guaranteed slow and drag it forward regularly
with hard settings of the clock. ( guaranteed no backward moves )

uwe


uwe





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